Share a keyboard and mouse with Synergy
The traditional method of sharing a keyboard and mouse across two or more systems is to use a KVM switch (keyboard, video, mouse), which is an electronic box into which all your cables go. By pressing a key sequence you are able to control other systems with a single keyboard and mouse.
I have used KVM switches for many years and apart from the initial cost, they can be cumbersome in terms of all those cables all over the place.
An electronic alternative is provided by Synergy, which is an open source product created by Chris Schoeneman. Instead of cables, Synergy connects your mouse and keyboard (not video) to multiple systems via IP Addresses, so all that's needed is a LAN connection.
Using the setup box, define which system(s) will fall under control when the mouse passes the edges of the screen and allocate a name and an IP Address
I currently control a Windows-based gateway box left-screen of my main workstation. It feels strange at first, losing control when the mouse disappears off screen but once you get used to it, it is a very convenient way to control multiple systems. The Scroll Lock key can be used to temporarily disable Synergy, for instance when playing games.
Although monitors can't be shared as with a traditional KVM switch, a bonus feature is that cut-and-paste works between connected machines. Very handy
The original Synergy covers 32-bit Windows up to XP and on Unix/Linux, X Windows version 11 revision 4 or up. Google Code have taken over current development with Synergy-plus, also released under the Gnu public licence. Plus implements bug fixes and support for Vista, Windows7 and 64-bit systems.
Installing and Using Synergy under Linux
Synergy official setup documentation
How to configure Synergy in six steps